Lecture 30 Flashcards
When are amino acids used for energy in our body and what pathway do they follow? What is a key step for humans?
Amino acids can be used as an energy source for our body, particularly during periods of fasting and is more important for carnivorous animals. The nitrogen of the amino acids can’t be oxidised by our (human) metabolism. We hence need to remove the nitrogen (deaminating) and then use the carbon skeleton via the normal metabolism pathways.
What are the methods of removing the amino groups from amino acids for energy production? What two processes can the carbon skeletons be used for?
Deamination generates a carbon skeleton for catabolic (breakdown) (or anabolic (making stuff)) reactions and a free amino group which is generally excreted. Sometimes this is done by releasing the amino groups to solution (e.g glutamate deamination done by glutamate dehydrogenase, which cleaves alpha amino group via redox to leave the carbon skeleton (alpha ketoglutarate)), other times it is done by transamination, this is done via aminotranferase enzymes which transfer the amino groups to a keto acid (which then becomes an amino acid).
What coenzyme is used in aminotransferase reactions and what does it do?
Aminotransferase reactions require pyridoxal phosphate (derived from vitamin B6) to act as a co enzyme, this will accept the amino group from the amino acid first and then transfer it to the keto acid.
What part of an amino acid are the keto acids and what is the difference?
The keto acids are essentially the carbon skeleton of the amino acid ( =O in place of NH3+), common examples are glutamate and alpha-ketogluatarate, aspartate and oxaloacetate and alanine with pyruvate. There are other common keto acids but they will require modification before they can enter metabolic pathways.
What does gluconeogenesis do? What other energy molecule can be produced from the reactant?
Glucose can be produced via gluconeogenesis from proteins in our body. Lipids can also be produced from amino acids.
How is excess nitrogen removed and why?
Excess nitrogen is removed via the liver in order to prevent toxicity due to ammonia acid/base properties and its ability to get across the blood brain barrier in the NH3 form (taking water with it). The liver does this by producing urea from the nitrogen and urinating it out when it is filtered by the kidneys.
What is oxidative phosphorylation? What is its link to the citric acid cycle and beta oxidation? What two processes are coupled and how?
Oxidative phosphorylation is our largest producer of ATP, in order to do this it requires the reduced coenzymes formed in the citric acid cycle and beta oxidation. It is the coupled process of electron transport via the electron transport chain and the phosphorylation of ADP to ATP via ATP-synthase. They are coupled via the electron transport chain making a proton gradient and ATP-synthase using it.
HOw do we seperate mitochondria from a solution and what can we show by adding detergent?
We isolate mitochondria from tissues by homogenisationing it in a buffered sucrose solution and then spinning it in a centrifuge to seperate the debris and nuclei and supernatant (stuff at the top) then take the supernatant and centrifuge it much faster to seperate a large group of mitochondria. If you add detergent we can then remove the outer mitochondrial membrane and the ETC will still function. This shows it occurs on the inner membrane.
What is the overview of the electric transport chain?
The electric transport chain works via carriers passing electrons between them, electrons from NADH and FADH2 are fed into this chain (oxidising them), the electrons will ultimately reduce molecular oxygen to water (oxygen is the terminal electron acceptor). The protons are pumped as the electrons are transported through the electron transport chain.
